We wish to explore clinical applications of the proto-zoological assay for biopterin while improving the assay's convenience, sensitivity, and specificity. Since purine is the biosynthetic precursor of biopterin, our demonstration that gout patients have elevated biopterin levels appears to support the spillover hypothesis-- that excess purine spills over into excess biopterin -- but more cases are needed to test this generalization. Since biopterin is the cofactor for enzymatic aromatic hydroxylation in the biosynthesis of catecholamines and the indoleamines serotonin and melatonin, the consequent elevated biopterin may contribute to the behavioral disorders characterizing the Lesch-Nyhan syndrome of children; we will try to obtain blood samples from such cases. Parkinsonism is characterized by dopamine deficiency in the nigrostriatal tract; we intend to determine whether biopterin deficiency contributes to dopamine deficiency. The elevated biopterin found by us in uremia and alcoholic liver disease also requires further case study. Are cells and tissues rich in biogenic amines necessarily rich in biopterin? We propose to assay the amine-rich neural tissues, adrenal medulla, and pineal gland. Validation of such a parallelism would encourage us to see whether elevated biopterin values exist in non-gout patients; this might aid diagnosis of such tumors as pheochromocytomas. The practicability of the assay raises the possiblity of anti- biopterin compounds in therapy: we will begin a search for anti-biopterins. We will also attempt to develop possible protozoan models for factors affecting biopterin synthesis, using the flagellate Ochromonas malhamensis -- a rich source of biopterin, and which can synthesize purines -- and Tetrahymena, which requires exogenous purine.